1. Field of the Invention
This invention is related in general to autonomous vehicles operating in a surface facility, such as a surface mine. In particular, the invention relates to a method for avoiding the formation of ruts and similar road damage caused by the repetitive passage of autonomously-guided vehicles over prescribed travel trajectories.
2. Description of the Related Art
Autonomous vehicles operating in a surface facility such as a mine are controlled by tracking the position of each vehicle in the system and by guiding the vehicle safely along a predetermined course. Guidance control signals may be generated from a central location, a peripheral position, other vehicles, or directly from within the vehicle. Typically, the position of the vehicle is continuously monitored and controlled by a central or satellite center transmitting control signals to the vehicle""s on-board computer, based on current mine conditions and in response to position information communicated by the vehicle. Alternatively, the vehicles""s own on-board computer can produce appropriate control signals to the vehicle as a function of its position and additional information received from external components of the guidance system. Knowing the current position of the vehicle with respect to known fixed obstacles and other mine equipment, the vehicle can be maneuvered to its destinations by the continuous control of its operating functions (for example, steering-wheel, accelerator and brake position of a truck). An on-board satellite-based positioning system (such as GPS) or an equivalent positioning unit (either of which can be supplemented with an inertial navigation system or the like) can be used to determine the current position of the vehicle, with an on-board transmitter/receiver unit to communicate with the control center, and on-board microprocessing and storage modules with appropriate hardware and software can also be used to effect the actual movement and guidance of the vehicle. Every operating function is manipulated to cause the vehicle to follow a predetermined trajectory that can be modified by current control instructions to meet particular up-to-date traffic conditions. Hazards are avoided by implementing a predetermined control response when a hazard is identified by the system. For example, if a potential obstacle is detected within a certain distance of the vehicle being monitored, the path of the vehicle is modified to avoid collision. Thus, for the purposes of this disclosure, the term xe2x80x9cautonomousxe2x80x9d is intended to refer to the availability of either on-board or off-board automated supervisory systems for controlling the movement of a vehicle.
Surface mines utilize a variety of work machines for excavating and transporting ore, grading and stabilizing roadways and slopes in the mine pit, and for providing all support functions necessary for the operation of a mine. In the past, most work and haulage machines have been human-operated, mobile pieces of equipment constantly being moved around the surface of the mine. Skilled operators ensure that each machine or vehicle is positioned in the right place and optimally oriented to perform its intended function while avoiding accidents and injury to people and property. In order to improve efficiency, much effort is currently under way to develop automated systems for controlling the operation of such work machines in surface mines and other environments. Therefore, this invention is described in the context of a surface mine operation, but its concept is applicable to any operation involving moving equipment (such as at waste sites and in underground mining, or in digging, shipping, trucking, and automotive operations) and should not be understood to be limited to surface mines.
As mentioned, the function of each autonomous vehicle in a surface mine is performed according to a predetermined trajectory related to its particular task and implemented by a guidance system through on-board GPS and two-way communication hardware. The roadways of mines are typically temporary and subject to frequent changes to adapt to varied operating conditions. Therefore, such roads normally consist of unpaved dirt routes that are easily damaged by vehicle traffic. In particular, the repetitive passage of autonomous vehicles over the same predetermined trajectories unavoidably causes ruts in the roads that can affect the efficiency and operation of the roads. Operators of manned vehicles can try and minimize this problem by avoiding existing cuts as they begin to appear on the road, thereby reduce the formation of deep ruts. Unmanned vehicles, on the other hand, are programmed to follow a preselected trajectory as precisely as possible, and much effort is dedicated, primarily for safety concerns and work efficiency, to ensure that deviations from that trajectory are minimized during the course of autonomous operation. Given the current state of the art, autonomous vehicles can be controlled to follow a path with maximum deviations in the order of centimeters. Thus, the formation of ruts is an inherent problem of autonomous-vehicle traffic on dirt roads. This invention is directed at reducing the rutting caused by the operation of such vehicles.
The primary objective of this invention is a guidance control system for reducing the formation of ruts in roadways travelled by autonomous vehicles in a mining or similar operation.
Another objective is an approach that can be integrated with existing guidance systems for autonomous-vehicle operation on dirt roads of industrial facilities, in particular surface mines.
Another goal is a system that is suitable for automated implementation with current autonomous equipment, in particular surface-mine haulage and mining equipment.
A final objective is a system that can be implemented economically according to the above stated criteria.
Therefore, according to these and other objectives, the present invention involves linking each autonomous vehicle and/or other moving equipment in a surface-mine facility to a control center for communicating data and control signals. The function of each autonomous vehicle is performed automatically by causing it to track a predetermined nominal trajectory related to its particular task and is implemented using on-board GPS and two-way communication hardware. The current position of the vehicle is continuously monitored and correlated to the position of potential hazards along its path, so that corrective action can be taken by implementing appropriate, predetermined control strategies.
According to the invention, the predetermined nominal trajectory for each vehicle is varied periodically within acceptable boundaries which define a travel corridor that ensures the continued safe and controlled operation of the vehicle within the system while avoiding the formation of ruts in the roadway. In an embodiment of the invention, the deviation is selected randomly from alternative trajectories that ensure a continuous and steady travel within the corridor containing the original nominal trajectory. By avoiding repeated passage precisely over the path of the nominal trajectory, wear on the road is greatly reduced and a more uniform surface is maintained for travel.
According to another embodiment of the invention, the guidance system may provide for multiple trajectories consisting of parallel paths to be used alternatively in order to avoid rutting of the roadway. In yet another, preferred embodiment, judiciously-selected, alternative trajectories are repeated periodically according to a predetermined schedule designed to avoid repetitive travel over the same precise path, and possibly also selected for optimal results under different terrain, environmental, and/or operational conditions.
According to another aspect of the invention, the shape and size of the corridor defining the boundaries for safe operation along the nominal trajectory are varied dynamically to increase operational flexibility within the safety requirements for current traffic conditions facing the vehicle as it performs its autonomous function along its predetermined path. For example, the width of the corridor may be increased when the autonomous vehicle is traveling alone, or decreased when it is in a high-traffic zone. Thus, the corridor may be dynamically adjusted for each vehicle as circumstances change during the performance of its autonomous function.
Various other purposes and advantages of the invention will become clear from its description in the specification that follows and from the novel features particularly pointed out in the appended claims. Therefore, to the accomplishment of the objectives described above, this invention consists of the features hereinafter illustrated in the drawings, fully described in the detailed description of the preferred embodiment and particularly pointed out in the claims. However, such drawings and description disclose but one of the various ways in which the invention may be practiced.